Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Tuesday will be a dynamic day in the mountains requiring you to manage very different avalanche problems. This includes dangerous conditions with slides that will be large enough to bury you. So, choose simple terrain that gives you plenty of options to minimize your exposure to steep open slopes.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    Very strong and gusty winds have been the defining feature of this storm, and they should continue into Tuesday. That means wind slabs may continue to grow and form in new locations. With such gusty winds, you may find this problem exists in some unusual locations like further off ridgelines, along the sides of gullies, and even down in the trees. Wind slabs may have even formed in some of you go-to “sheltered” spots.  At this point, there could be several potential weak layers within wind drifted snow. So, you could see shallow or very deep slabs release. This isn’t our normal wind slabs issue and not one you want to try to outsmart. Unless you’re standing on a scoured slope, anticipate wind slabs on any steep area. Look for blowing snow, sharp drifts, and firmer slabs to highlight potential wind-loaded terrain.

    While we don’t expect a natural avalanche cycle Tuesday, you could see slides occur, especially at upper elevations and in complex terrain. This isn’t a time to linger under steep open slopes especially when they are capped by weak overhanging cornices.

    (4/2/2022) Example: Signs of possible wind slabs can help you anticipate possible wind slab locations. Photo: Dallas Glass

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    It probably won’t take much sunshine on Tuesday afternoon to set off a loose wet avalanche cycle. The key to this problem will be the cloud cover. If you see significant sunbreaks, immediately think “loose wet avalanches.” That means the time has come to get out from under any steep sunny slope. With quite a bit of new snow on the ground around the Pass, some of these slides could grow large and run far distances. So, don’t be standing in their way. If the skies stay mostly cloudy, this problem likely won’t be an issue. 

    At lower elevations, less new snow will limit the potential size and consequences of these avalanches, but they will still occur. Take care to make sure one of these slides doesn’t push you into a creek or gully where even a smaller avalanche can bury you.

    (12/21/2021)

    Example: A large natural loose wet avalanche when the sun came out following a storm back in December. 

    Photo: Charlotte Guard

Avalanche Discussion

The storm is still going at Snoqualmie Pass and more snow is expected Monday night and Tuesday. So far, snow totals have varied widely by elevation. Our weather stations, as of 5pm (Tues), have recorded 8-9 inches at pass level, with 28 inches at the top of Alpental. Winds over the course of the storm have been strong and very gusty. All this snow accumulated over the Early April Crust. This is a prominent snowpack marker that you can find on nearly all aspects and elevations. Prior to this storm, 4-6 inches of snow capped this crust on some shaded slopes. Not only can this layer help you determine how much snow fell, but it will also focus your observations on the upper snowpack. We don’t expect avalanches to involve snow below this crust. 

On Tuesday quite a bit of uncertainty exists in the weather forecast and consequently the avalanche forecast. Not only do we have questions about the sky, but also precipitation. A Puget Sound Convergence Zone could bring locally heavier snowfall in the afternoon. Remember natural avalanches most often occur during periods of heavy snow and wind loading.

Regioni coperte